How The Morning-After Pill Works

Mitt Romney referred to morning after-pills as 'abortive pills.' The FDA-approved label on Plan B indicates it may prevent fertilized eggs from implanting in a woman's uterus. Dr. Kristina Gemzell-Danielsson, an obstetrics and gynecology professor at Karolinska Institute, discusses the growing scientific evidence to the contrary.

This is SCIENCE FRIDAY. I'm Ira Flatow. Morning-after pills are no stranger to controversy. Remember when some pharmacists refused to fill prescriptions for Plan B, or more recently when the federal government limited access to them for young teens? Election-year politics is once again fueling the debate over morning-after pills and claims that they are abortion-inducing drugs.

On the campaign trail, Mitt Romney called emergency contraceptives abortive pills, and other conservatives have echoed the sentiment. And to add to the confusion, the label inside every box of emergency contraceptive states that it may prevent the implantation of a fertilized egg in a woman's uterus, something religious groups, some of them, say amounts to abortion.

But a number of scientists say the issue has become so politicized that we're ignoring the real facts. They say study after study have shown that emergency contraceptives like Plan B inhibit or delay ovulation, they do not interfere with implantation.

Dr. Kristina Gemzell-Danielsson has conducted some of this research. She's professor and chair of the Division of Obstetrics and Gynecology at Karolinska Institute in Sweden, and she joins us from Bergen, Norway. Welcome to SCIENCE FRIDAY.

KRISTINA GEMZELL-DANIELSSON: Thank you.

FLATOW: Are these abortion pills?

GEMZELL-DANIELSSON: No, they're not. They are contraceptive pills.

FLATOW: Tell us how they work.

GEMZELL-DANIELSSON: Well, they work to postpone or to prevent ovulation, and they have absolutely no effect after ovulation.

GEMZELL-DANIELSSON: Yeah, so it depends on when you take it. You have to be aware when the fertile window is. So it's five days before ovulation and then about maximum one day after ovulation. And if you take it before the LH surge has started, then it works by either blocking follicular development and ovulation or by postponing it.

But if LH has started to rise, then it's too late, and it has no effect, and ovulation will occur. And it has no effect after ovulation, no effect on the fallopian tube or on the endometrium, that is the uterine lining. And actually if a woman has miscalculated, so she's already pregnant, it has no negative effect on the pregnancy, on the fetus or on the newborn baby. And it can't interrupt a pregnancy, but it has absolutely no effect.

FLATOW: So exactly what does it do?

GEMZELL-DANIELSSON: Well, it - if taken before LH has started to rise, it prevents the LH surge, and that's why ovulation doesn't occur. But has LH started to rise, then it has no further effect. This is Plan B, which consists of (unintelligible). There is a difference. There is another pill, Ella, and it's called Ella-1 in Europe, which can actually work even after LH has started to rise because it has a local effect also in the follicle. So...

FLATOW: And LH is a hormone?

GEMZELL-DANIELSSON: LH is - it's the trigger. It's a hormone. It's the trigger. So that's what triggers ovulation, yes.

FLATOW: So this prevents the hormone from triggering ovulation.

GEMZELL-DANIELSSON: Exactly. And Ella has also, in addition, a local effect in the follicle. So it can prevent the rupture of the follicle, that is ovulation. So the window of action is a little bit wider. That's why it's a bit more effective. But again, it can't work after ovulation has occurred. And if would, it would be more effective. So in a way, it would have been good, but that's not happening with the current alternatives.

FLATOW: You were involved in the WHO trials that eventually led to the FDA approval of Plan B. Why does the label on the Plan B box say it may inhibit implantation?

GEMZELL-DANIELSSON: Yeah, I mean, this - that's regulatory issues. When we did the study, there were two large multicenter, multinational trials, but the main outcome of those studies were efficacy and side effects. So mechanism of action was not involved in those trials. And to register the pill, it was not required to study the mechanism of action. So that was just assumption, and I think it was also wishful thinking, that it would be more effective than it is.

So if it - I mean, if the mechanism was to prevent ovulation if used prior to ovulation and then to prevent implantation if used after ovulation, then the efficacy would be higher. So I think initially that was the wish.

But then when we also started to study mechanism of action, we saw clearly that it had no effect after ovulation.

FLATOW: So the language was written before you even knew how it worked.

GEMZELL-DANIELSSON: Yes, that's true.

FLATOW: Does that seem a little backwards?

GEMZELL-DANIELSSON: Yes.

FLATOW: Or is it more politics than backwards?

GEMZELL-DANIELSSON: Well, that's regulatory issues. So really I don't know exactly how it works at the FDA, but the problem is it caused a lot of damage because people believed that what is in the label is also the absolute truth or the science.

FLATOW: So does it need any more studies, or is it pretty well-understood, the mechanism?

GEMZELL-DANIELSSON: No, I think it would - it doesn't need more studies, no, not in that way because that's absolutely clear.

FLATOW: So as you said before, there is, in your mind and in the mind of the people, most people who are involved in this kind of work, it really is a great fallacy to call it an abortion pill?

GEMZELL-DANIELSSON: Yeah, that's totally wrong. It's really misleading. So it may also prevent some women from using it, which is really sad. Or it may be that women believe that it can induce an abortion, and then they are - which may cause problems. So I think it's important to know how it works.

FLATOW: And also on a slightly connected note, it is not something that's going to prevent you from getting a sexually transmitted disease by taking this pill, either.

GEMZELL-DANIELSSON: No, it's not, but on the other hand, there are studies, well-done studies to show that using emergency contraception doesn't increase the rate of sexually transmitted disease because you use it after the unprotected intercourse. So that has already happened, sort of.

FLATOW: So there's still need to have safe sex even though you're using...

GEMZELL-DANIELSSON: Well, ideally women and couples should use the most effective method, but there are - we know that reality is not always perfect. So there is a need for this backup contraceptive method. And we have - I mean, there are also well-done studies to show that women who use it, they actually take responsibility. So it's not only unprotected intercourse, it could be after rape, or it could be after other methods have failed.

FLATOW: Thank you very much, Dr. Gemzell-Danielsson, for taking time to be with us today.

GEMZELL-DANIELSSON: Thank you.

FLATOW: Dr. Kristina Gemzell-Danielsson is professor and chair of the Division of Obstetrics and Gynecology at Karolinska Institute in Sweden.

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